Concerning reaction time training and measurement, I just came back from a Large Sporting Goods trade show and got to test this item called the "Hitmaster"
It can measure your reaction time in thousandths of a second
1. Reaction Time – Select a 2-to 5-second random delay or instant beep. Your reaction time to the beep is displayed in thousandths of a second, up to a maximum of 2 seconds.
You can Record up to 20 reaction times, which can then be reviewed on the display. Review your average and fastest reaction times, and export to a computer. These countdown options are designed to train for a series of impact combinations, or to improve rapid impacts in short bursts of time. These options can also be used in competitions to determine who can make the most impacts in a matter of seconds.
2. Sparring Rounds – Designed to simulate competitive sessions encountered in many contact sports. Select 2-or-3-minute round duration, and select 1 to 5 sparring rounds 1-minute rest periods. One beep starts each round and two beeps signals the end of rounds and end of session.
The HitMaster Controller records the number of hits in up to 3 zones on the pad for the entire session and then lets you review your session round by round with the number of hits per zone being displayed.
Session results can be exported to a computer for future review and tracking.
3. Countdown Timer – Select from 1, 5, 10, or 60 second time periods to measure your speed. Press start and the HitMaster Controller beeps to begin your countdown timer session. The number of your impacts to the HitPad is recorded in all 3 zones (A, B or C) and displayed at the end of your session. Up to 5 sessions can be recorded and exported for tracking your progress over time.
It is a unique training aid, and after trying it I must say it appears to work as advertised. It attaches to any heavy bag of similiar target ( punch bobs and all those....) They say to keep your fist at least 12 inches from the pad, and if you are going to measure numerous attempts, you need to keep your fist or foot the same distance away for all attempts.
I also found out that "reaction time" competitions will soon begin to be a part of regional and national martial arts tournaments, and this device will be used as the method of measurement. so if you and your students go to tournaments a want to enter in this division, this is the device they will be tested on.
It might be a little high in cost, but it is NOT a toy and if you think you're fast this will give you some reliable measurements.
It looks to be a legitimate training device if you want feedback on the speed of your reactions.